Bushfire ash & debris as well as drought now killing fish in NSW coastal and inland rivers

"Fish kills are defined as a sudden mass mortality of wild fish. In NSW we are likely to see further severe fish kills across coastal and inland catchments during the summer of 2019/20....Fish can be directly impacted during fires through extreme high temperatures, loss of habitat, or be threatened from rapid declines in water quality if rainfall occurs in recently burnt areas. Run-off from rainfall events can wash large amounts of ash and sediment into rivers following fires, causing rapid drops in oxygen levels and threatening the survival of fish populations." [NSW Dept of Primary Industries]

The upper reaches of the Clarence River have been badly stressed by low water flows since 2018, so when bushfires began to eat their way through the severely drought affected Clarence Valley in mid-2019 it was obvious that the rolling impacts wouldn't stop when the fires diminished or when rain fell.

There has been a fish kill at Big Fish Flat, an area known for the protected eastern freshwater cod now only found in parts of this river system and commonly known as Clarence River Cod.

The most likely cause of this kill is bushfire ash entering a river which has all but ceased to flow - turning what water there is into a toxic brew.

At Baryulgil on the Clarence est. 1,000 fish died due to low dissolved oxygen within an isolated pool receiving minimal inflows due to drought conditions.

There was also a fish kill on the Mann River, a major tributary of the Clarence which reportedly coincided with ash in the water.

Two fish kills were experienced to the north at Emigrant Creek at Tintenbar in the Ballina Shire and the Brunswick River near Byron Bay - possibly due to low dissolved oxygen within an isolated pool and minimal freshwater inflows. 

Another fish kill occurred to the south on an 8km stretch of the Macleay River where locals describe the bushfire ash and burned debris turning that river's water into a thick sludge killing hundreds of thousands including Australian Bass, Bull Trout, Freshwater Mullet, Eel-tailed Catfish and Eels.

The Guardian, 17 January 2020: Results of a fish kill in the Macleay River in northern New South Wales, which locals said was like ‘cake mix’. Photograph: Larry Newberry

Similarly bushfire affected water ways in the NSW-Qld Border Rivers system appear to have been similarly affected by run-off from the fire grounds and reported fish kills there are being investigated.

All in all a total of 23 coastal and 17 inland NSW waterways have experienced small to large fish kills to date during the 2019-20 bushfire season.